Interest in mobile computing, a relatively new field, has been largely driven by the miniaturization of electronics and by the focus in technical literature on wireless communications and personal communication services (PCS). As mobile computing machines continue to shrink in size, it has become evident that a practical implementation of "data-oriented" PCS will require a delicate balance between the competing objectives of reduced size and acceptable system performance. Examples of currently available mobile computing devices include modem-equipped notebook computers and personal digital assistants (PDAs)
PCMCIA (Personal Computer Memory Card International Association) cards advantageously provide the notebook computer or PDA user with an opportunity to enhance or to expand the unit's basic capabilities where space is at a premium. Although PCMCIA cards may be utilized for such diverse applications as modems, exterior storage devices, sound cards, and printers, they are particularly well suited for wireless communications applications in which a communications link must be established between the mobile computer and a remote processing device or network of such processing devices.
Reductions in the size of portable or mobile computing machines have come at the expense of certain resource limitations which, in turn, substantially limit system performance. One obvious example of a resource constraint which directly impacts the operating performance of mobile computers is battery size. Smaller machines carry smaller batteries. To support "uninterrupted" operation for 4-6 hours, a typical performance benchmark, power consumption is minimized by setting the clock speed below a given rate. Other performance-affecting resource limitations of mobile computing machines relate to memory size, CPU cycles, wireless transmission bandwidth, display size, and the like. In some cases, there is a dependency between the limitations. For example, smaller battery capacity may necessitate less wireless bandwidth.